1. Field of the Invention
The present invention relates to a liquid dispensing and/or aspirating device that is operated manually.
2. Description of Related Art
Dispensing devices relevant to the present invention include pipette systems with repeating pipettes operated by direct displacement (positive displacement pipette) or displacement with a cushion of air (air displacement pipette), or metering devices of a metering system operating with positive displacement or air displacement.
Manually operated repeating pipettes are pipettes which are operated by hand and are connected to a large-volume syringe from which a small partial amount can be metered into a receiving container by operation of the actuating element. Repeating pipettes are used for series tests, especially in conjunction with a plurality of receiving containers, often with so-called titration plates.
There are manually operated repeating pipettes in which a plunger adjusting device is operated by stepping mechanics and the plunger in the syringe is displaced to the desired specific extent in each metering step. Conventional volumes to be pipetted, i.e., metered amounts, would be e.g. 100 μto 500 μl, where a typical syringe has a filling volume which corresponds to 10 to 100 times the desired metering amount.
However, an more advantageous repeating pipette is operated by an electric motor where the electric motor drive is controlled by operation of the actuating element on the pipette housing, and the plunger adjusting device is moved to the desired extent. A repeating pipette operated by an electric motor is especially convenient to operate because of the electric motor drive. The control electronics provided to control the electric motor drive offer the possibility of not only accurately preselecting the metered quantity, but also preselecting a metering interval for a plurality of metering operations of identical metered amounts to be carried out in succession. Therefore, in such a repeating pipette (positive displacement) which is known from practice, the desired metering interval is adjusted in an adjustment range from 0.1 to 1.0 sec by means of programming keys on the programming element, adjustment increments of 0.1 sec being possible. In another system known from practice, a repeating pipette designed as an air displacement pipette is provided, and a metering interval between 0.1 sec and 10.0 sec can be entered for this pipette.
If an operating person has the impression from previous activity that a metering interval of 0.4 sec is feasible for example, then this operating person will set this metering interval by means of the programming element. If the operating person then begins the metering, the operating person can keep the actuating element continuously in operation after the start of the metering cycle. The individual metering operations then take place automatically at intervals according to the adjusted metering interval, i.e., at an interval of 0.4 sec, in this example. The operating person then needs only be sure to always move the repeating pipette over a new receiving vessel in this cycle. This eliminates individual operation of the actuating element which would otherwise be necessary to trigger the individual metering operation. This greatly increases working speed.
Similar issues and concerns such as those encountered with repeating pipettes also occur in general with metering equipment that is operated by electric motor but is actuated by hand when repeated automatic metering operations are to be carried out with the metering device. In this regard, reference is made to the German patent DE 195 13 023 C2 which shows the state of the art for metering devices. They are known in particular as bottle metering devices or bottle titraters. In addition, as already indicated above, a similar issues and concerns also arises with manually operated aspirating devices for liquids and combined devices which combine liquid aspiration and dispensing functions.
A pipetting device having a memory function is known, for example, from the German application DE 44 36 595 A1. This pipetting device has a programming element which can assume a manual position, a memory setting position and a memory operating position. If the programming element is in the memory setting position, actuation of the actuating element results in the fact that a storage volume, which is determined by the operating person, can be aspirated (or dispensed). This storage volume, which is predetermined by the operating person, is then stored in the memory in the control electronics. Then if the programming element is switched to the memory operation position, subsequent manual actuation of the actuating element results in automatic dispensing (or aspiration) of a quantity of liquid of the amount stored previously. Actuation of the actuating element then serves only to trigger the dispensing step or the aspiration step but not to determine its duration.
There is also a repeating pipette operated by electric motor disclosed in the International applications WO 00/51739 A and WO 00/51738 A which has an especially ergonomically advantageous arrangement of actuating elements near a display. However, these references fail to disclose details regarding the functioning with regard to receiving and dispensing partial quantities of liquid.
Finally, there is also a known repeatedly actuated metering device as disclosed in the “Compudil” brochure dated Apr. 12, 1984 which can be programmed in various programs by a programming device. With regard to dispensing partial quantities of liquid, the functioning corresponds to that of the pipetting device described previously.
With the prior art described above, the individual process step is triggered by manual actuation of the actuating element. However, these references do not disclose automatic repeated successive triggering of process steps in a certain preadjustable process interval. In this regard, there is an unfulfilled need for a dispensing and/or aspirating device for liquids that allows automatic repeated successive triggering of process steps in the certain preadjustable process interval.